Synthesis and Spark Plasma Sintering of Si3N4–ZrN Self-Healing Composites

A Si3N4-ZrN wear-resistant self-healing composite material was developed. Si3N4-ZrN composite ultrafine powders were synthesized at a temperature of 1200 degrees C via solid-state reactions without milling and densified by spark plasma sintering at 1650 degrees C to a relative density of 97 +/- 0.5%. Balls 13.494 mm in diameter for ball bearings manufactured by spark plasma sintering had a fine-grained structure with a grain size of 200-500 nm, Vickers hardness of 22.5 +/- 1.8 GPa, and indentation fracture toughness of 6.2 +/- 0.4 MPa. The tribological properties of the composite were investigated under static and dynamic loading. The self-healing capability of the Si3N4-ZrN composite was evaluated in the temperature range 500-550 degrees C. High-temperature three-point bending tests of notched specimens showed a bending strength of 383 +/- 21 MPa at room temperature and 413 +/- 30 MPa at 500 degrees C, which confirmed the self-healing of the composite.